Um, no Actually I am sort of hoping for you to come up with a cool $5 PIC-based interface in the near future My experience with PICs is still next to zero, but I intend to learn more about them, e.g. by building a little development kit and starting off with a simple project.

Well, although I learned PIC programming at school, it's now nearly ten years ago and I have no experience and no material to program PICs, so definitely, I'll do it with a PC serial port or I won't do it at all... By the way, you mentioned "D2B" but are you sure it's the protocol used here ? 5 minutes google search for D2B makes me think it's a very generic protocol, much more than what I'd expect for a simple CD-changer/headunit dialog...

The OEM display in my Clio's dash is somewhat limited, as it only displays track# and cd#, so no remaining time or anything. I guess the ppl of connects2.com have found a way to mimic a single cd with a single endless track. Once I select the cd changer as a source, the HU permanently displays "CD1 - TRACK 1".
Somehow I am glad my display is limited

The more I think about the problem, the more I think it would make sense that once the head unit source is switched to a CD changer, it delegates all CD handling to the changer and only "passes through" commands from its front panel to the changer and replies back to its display. In that case, the only thing that *has* to be implemented is the "handshake" protocol so that the head unit always thinks that there is a changer present. Then maybe send a static "CD 1 - Trank 1 - Time 0:00" and off we go...

By the way, you mentioned "D2B" but are you sure it's the protocol used here ? 5 minutes google search for D2B makes me think it's a very generic protocol, much more than what I'd expect for a simple CD-changer/headunit dialog...

I vaguely remember reading something on planeterenault.com about the highly popular CHM 604 mp3 cd changer using the D2B protocol. It might as well have been a German site, I can't remember

Since I've already settled for using my 89 euro Connects2 adapter, I was pondering some kind of smart processor driven interface between stalk control, PC and HU. Purpose of the interface would be to relay stalk commands to the HU by default, unless a certain stalk switch combination or sequence is given (e.g. pressing "source up" and "source down" simultaneously). The interface should then disconnect from the HU and pass controls to the PC instead. By using the interface to translate stalk keypresses into serial data (like an IR remote control), you could then use a serial port and Girder to control whatever application you like

BTW, FYI, here are the main components used in the Connects2 interface (I did some reverse engineering on the hardware).

UART control port:
ST72C314J4 (some flash microcontroller), linked to a BA8270F ("Bus Interface for Car Audio") which connects to the HU's UART lines.

Datasheets of these chips can be found online. Let me know if you have trouble finding them. Given your theory about the protocol, the BA8270F might be particularly interesting, as the datasheet states that it's an interface *master*

My best bet for now would to fix the screen to a big clip that would "bite" the top of the Scenic's dashboard to have the screen almost at the same place as the factory GPS option

I am also avoiding any mods to my Clio here. Furthermore, I wanted the monitor to be removable at all costs. I am quite fond of this (anodized!) aluminum bracket that I've made for my 7" lilliput. The ugly black round cable will soon be removed, as all necessary connections will eventually be made thru the 15 pin D-sub connector which plugs into a connector that I've mounted into a little coins tray in my dash (I bought the original Renault spare part ).

The flatcable will go through a slot in the back of the monitor and be soldered internally. Will post more pics soon.

I was pondering some kind of smart processor driven interface between stalk control, PC and HU. Purpose of the interface would be to relay stalk commands to the HU by default, unless a certain stalk switch combination or sequence is given (e.g. pressing "source up" and "source down" simultaneously). The interface should then disconnect from the HU and pass controls to the PC instead. By using the interface to translate stalk keypresses into serial data (like an IR remote control), you could then use a serial port and Girder to control whatever application you like

I see... Interesting idea indeed. The source up+down might not be possible on all units (mechanically, on both my headunit and my stalk controls, the up and down are mutually exclusive) but I see the idea.

BTW, FYI, here are the main components used in the Connects2 interface (I did some reverse engineering on the hardware).
Analog-to-SPDIF:
TL064 (stereo AF amp), linked to a 5331AKS (stereo A/D converter with serial output), linked to a CS8405A (SPDIF encoder), linked to the HU's SPDIF input.

That's interesting for anyone wanting just to connect a mp3 player to the head unit letting the control cables run to the changer as I did...

UART control port:
ST72C314J4 (some flash microcontroller), linked to a BA8270F ("Bus Interface for Car Audio") which connects to the HU's UART lines.

Datasheets of these chips can be found online. Let me know if you have trouble finding them. Given your theory about the protocol, the BA8270F might be particularly interesting, as the datasheet states that it's an interface *master*

Well, yes...
Unfortunately, this doesn't give explanations about the actual protocol, but better than nothing. Thanks for all this information, I just cross-posted it to planeterenault.com - hope you won't mind, I should have asked before ...

Furthermore, how can I get the audio line-in (and the mic input) of the epia to be mixed into the SPDIF output?

EDIT: I did a search on the analog input issue. There doesn't seem to be a solution yet. A software pass-thru might do the trick, but it will increase cpu load. Anyone?

After a bit of search, I found the "FullDuplexFilter" sample of the DirectX sdk : It records what comes in through the Mic and plays it back after 1 second.
I don't have a Windows development environment handy, but I think it'd be fairly easy to modify it to have it sample the line-in also, reduce the delay to the minimum and remove all the selection part of the GUI.

I believe its CPU use would be next to zero as it only copies incoming buffers to the output without any processing...

Sorry for the late reply, I was on holiday.
Great find, Vicne -- I'm not sure which frontend you are using, but maybe we can ask Guino to add full duplex support to his RoadRunner. I don't have any development stuff installed either. Actually I'm not much of a programmer at all. I got stuck in the Motorola 6502/6809/68000/68HC11 assembly era